Electromagnetic switch mounting



2 Sheets-Sheet 1 mm .P

Q mu v :F N hw Q Sept. 1939- E. L. HOFFMANN ELECTROMAGNETIC SWITCHMOUNTING Filed Dec. 50, 1936 p 26, 1939- E. L. HOFFMANN 2,174,086

ELECTROMAGNET IC SWITCH MOUNTING Filed Dec. 30, 1936 2 Sheets-Sheet 2INSULATION &2- 44 l a 9 I66 .ZZMEQ 561.15 fioFFAm/v/v.

Patented Sept. 26, 1939 UNITED STATES PATENT OFFICE ELECTROMAGNETICSWITCH MOUNTING Application December 30, 1936, Serial No. 118,209

5 Claims.

This invention relates to an automatic frequency selector, and moreparticularly to an automatic switching mechanism which is adapted toselectively connect a plurality of frequency changing elements indesired position in a high frequency apparatus. The invention isparticularly suitable for use in conjunction with a radio broadcastreceiving set.

In high frequency apparatus which is adapted to operate at a number ofdifferent frequencies, such for example, as radio receiving set, thechange from one frequency setting to another is generally accomplishedthrough the use of a number of variable condensers. Although the usualradio receiving set is arranged for adjustment to a very large number ofdifferent frequency settings, in practice it has been found that theequipment is usually operated at one of a relatively few frequencysettings. That is to say, the programs which are provided by four orfive local stations are generally suflicient to satisfy the averagelistener. Although the manipulation of the control knobs of a radioreceiving set is relatively simple, it nevertheless has been found to bea considerable nuisance on many occasions. This is particularly truewhere the radio receiving equipment is mounted in an automobile wherethe person operating the radio receiving equipment must direct a greaterpart of his attention to the driving of the machine.

It is an object of the present invention to provide a novel automaticfrequency selector which will enable the operator of high frequencyapparatus to change from one frequency setting to another with a minimumof effort and attention.

Another object of this invention is to provide an automatic frequencyselector which is economical to manufacture, which is eflicient inoperation, and which is rugged and reliable in use.

A further object of this invention is to provide a novel automaticfrequency selector wherein one of a predetermined number of frequencysettings may be obtained by depressing one of a corresponding number ofpush button switches.

A still further object of this invention is to provide a novel automaticselector switch construction having a frame construction made from asingle stamping.

Another and further object of this invention is to provide a novelautomatic selector switch mechanism having a novel arrangement ofelements.

Another and still further object of this invention is to provide a pawland ratchet drive mechanism which permits movement of the pawl prior tothe time when the pawl engages the ratchet to do work thereupon.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My invention 5itself, however, both as to its organization and manner of construction,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying lo drawings, in which:

Figure 1 is a diagrammatic view of one embodiment of my inventionwherein a plurality of relatively fixed condensers, such as trimmercondensers, are adapted to be selectively shunted across the three unitsof a gang condenser;

Figure 2 is a front elevational view partly in cross sectionillustrating the automatic selector switch mechanism;

Figure 3 is a side elevational view partly in cross section of theautomatic selector switch mechanism shown in Figure 2; and

Figures 4 and 5 illustrate how the armature mechanism is mounted on itssupport.

Referring now to Figure 1 of the drawings, the arrangement illustratedtherein includes a three unit gang condenser [0 having rotor plates I I,I2, and I3, and stators I4, I5, and I6. Although only one rotor plateand two stator plates have been illustrated for each condenser, it is ofcourse to be understood that any number of rotor plates and statorplates may be employed, the number being reduced here merely for thepurpose of simplicity of illustration. Three groups of trimmercondensers I'I, I8, and I9 are associated with gang condenser I0.Trimmer condenser group I1 includes five trimmer condensers 20, 2|, 22,23, and 24, each of which has one side thereof connected to a commonlead 25, which connects this group of condensers to stator I4. Trimmercon- 40 denser group I8 includes five trimmer condensers 26, 21, 28, 29,and 30, each of which has one side thereof connected to a common lead 3|which connects this group to stator I5. Trimmer condenser group I9includes five trimmer condensers 32, 33, 34, 35 and 36, each of whichhas one side thereof connected to a common lead 31 which connects thisgroup to stator I6. The opposite sides of the condensers of groups I'I,I8, and I9 are adapted to be selectively connected to rotors II, I2, andI3 through lead wires 38, 39, and 40 respectively by a selector switchmechanism presently to be described.

The rotary selector switch by which a condenser is selected from each ofcondenser groups 5 il, l 9, and l9 and connected across the associatedunits of gang condenser l9 will now be described. A plurality ofmultiple contact rotary switches 4 l, 42, and 49 are mounted with theirrespective movable contact elements 44, 45, and 49 on a common shaft 4i.As will be observed from an inspection of the drawings, movable contactelements 44, 45, and 49 have different configurations for a reason whichwill presently appear. Rotary switch 4i is provided with twelveannularly disposed, substantially equally spaced stationary contacts 49,49, 59, 5E, 52, 53, 54, 95, 56, 51, 58, and 59. Movable contact element44 of switch ll is divided into two portions 90 and 6! which areelectrically insulated from each other. Portion 99 includes asubstantially semi-circular conducting strip 92 and a projectingconducting tongue 93. Portion Si is similarly provided with asubstantially semi-circular strip 94 and a conducting tongue 95.Stationary contacts 49 to 59 inclusive are so disposed that they willengage one of the projecting conducting tongues when that tongue passesbeneath it but will not engage at any time circular portions 62 and 94.

Two additional stationary contacts 69 and 61 disposed diametricallyopposite each other are arranged to engage one or the other of circularconducting strips 92 and 64 at all times, It will thus be apparent thatstationary contact 95 may be electrically connected to one of stationarycon tacts 49, 49, 59, 9!, 52, or 59, depending upon the position ofprojecting conducting tongues 99 and 65, while stationary contact 97 maybe connected to one of the stationary contacts 54, 55, 56, 51, 99, and59.

As will be seen from the drawings, stationary contacts 49 to 59inclusive are electrically connected to trimmer condensers 29 to 24inclusive, while stationary contacts 54 to 59 inclusive are electricallyconnected to trimmer condensers 26 to 39 inclusive. Stationary contact69 is electrically connected through conductor 38 to rotor ll of gangcondenser it, while stationary contact is electrically connected throughconductor 39 to rotor l2 of gang condenser l9.

Movable contact element 45 of switch 42 is similar in shape to movablecontact element 44 of switch 4i, with the exception that it is notsevered into two complementary halves. Movable contact element 45includes a completely circular conducting portion 99 and two projectingconducting tongues 69 and 79. Six stationary contact elements ll, l2,l9, l4, l5, and '06 are substantially equally spaced about movablecontact element 45 throughout an angle of substantially 180". Thesestationary contacts are disposed in relation to movable contact element45 so that they will at no time engage circular conducting portion butwill engage either tongue 69 or tongue 719 as it passes therebeneath. Anadditional stationary contact W is arranged to engage circularconducting portion 99 at all times. Stationary contacts 12 to 76inclusive are electrically connected to trimmer condensers 32 to 99inclusive, while stationary contact i1 is electrically connected throughconductor 49 to rotor E9 of gang condenser ill, in a manner similar tothat described in connection with rotary switch 4i. As one or the otheror" conducting tongues 99 or 79 engage one of the stationary contacts Hto l9 inclusive that contact is electrically connected to stationarycontact l! and hence to rotor l3.

Movable contact element 46 of switch 43 includes a circular conductingstrip 79 which is provid'ed with two diametrically opposed cut-outportions 19 and 89. Six stationary contacts 8i,

82, 83, 84, 85, and 86 are disposed about circular contact element 45throughout an angle of substantially 180. In contradistinction to thearrangement of rotary switches 4| and 42, stationary contacts 8! to 89inclusive are arranged to electrically engage circular conducting strip18 at all times, except when one of the two cut-out portions 79 and 99fall therebeneath. An additional stationary contact element 8'! whichextends further into the rotary switch 43 is arranged to engage circularconducting strip 18 at all times irrespective of the position of cut-outportions 19 and 80.

Switch 43 is the switch by which the angular position of shaft 41 iscontrolled. Insofar as the explanation of Figure l is concerned, it isto be understood that shaft 47, upon which movable contact elements 44-,45, and 49 are secured, will be rotated by means of a pawl and ratchetdrive (the ratchet not being shown in Figure 1 for purposes ofsimplicity of illustration). The pawl and ratchet drive, or, as it issometimes called, the stepping mechanism, includes a solenoid 88, asolenoid armature 89 which is mounted for angular movement in closeproximity to the upper end of solenoid 89, a pawl 99 connected to thefree end of armature 99, and a ratchet (not shown in Figure 1) which ismounted on shaft 41 and arranged to be engaged and driven by pawl 99.The lower end of solenoid 88 is electrically connected to stationarycontact 8'! of switch 43. The upper end of solenoid 88 is electricallyconnected to a leaf spring contact element 9| secured to the upper partof armature 89 which is adapted to engage a stationary contact 92 whenarmature 89 is in its uppermost position and to be disengaged therefromwhen armature 89 is in its lowermost position. As will now be explained,solenoid 88 is adapted to be energized from a suitable source ofelectric energy 93 through switch 43 and contacts 9| and 92.

Electrically connected to the lower end of energy source 93 are sixparallel connected push button switches 94, 95, 96, 91, 98, and 99. Theopposite sides of push button switches 94 to 99 inclusive areelectrically connected to stationary contacts 8| to 86 inclusive ofrotary switch 43. It will thus be apparent that if one of push buttonswitches 94 to 99 inclusive is depressed and its cooperating stationarycontact on rotary switch 43 is in engagement with circular conductingstrip 18, solenoid 88 will be energized and armature 89 will be moveddownwardly. Downward movement of armature 89 causes contact 9| to breakfrom contact 92, and solenoid 88 is deenergized. Biasing spring I90connected to armature 89 causes the return of armature 89 to itsuppermost position, and contact 9| again engages contact 92, whereuponif the push button switch is still depressed and its cooperatingstationary contact on switch 43 is still in engage ment with circularconducting strip "i8, solenoid 88 is again energized, thereby causingarmature 99 to be again depressed. Each time armature 99 is moveddownwardly, pawl 99 effects engagement with its cooperating ratchetwheel (not shown in Figure 1), thereby causing rotation of shaft 41.Assuming for the moment that push button switch 9'! is the switch whichis depressed, it will be readily understood that solenoid 88 willcontinue to effect rotation of shaft 4'! until cut-out portion 19 fallsopposite stationary contact 84. At this time the rotational movement ofshaft 47 will cease, irrespective of whether contact 91 is held down ornot, since the electrical energization circuit to solenoid 88 iseffectively broken in switch 43.

It is to be remembered. that as shaft 41 rotates movable con-tactelements 44 and 45 of switches 4| and 42 are also being rotated. Thus,when cut-out portion 18 of switch 43 moves into position oppositestationary contact 84, conducting tongue 10 of switch 42 has moved intoengagement with stationary contact 14, conducting tongue 05 has movedinto engagement with stationary contact 51, and conducting tongue 63 hasmoved into engagement with stationary contact 5|. Engagement ofconducting tongue 10 with stationary contact 14 causes trimmer condenser34 to be connected across the rear unit of gang condenser I0, whileengagement of tongue '65 with stationary contact 51 causes trimmercondenser 28 to be connected across the middle unit of gang condenserI0, and engagement of tongue 63 with stationary contact 5| causestrimmer condenser 22 to be connected across the front unit of gangcondenser I0. It will thus be readily understood that when push button94 is depressed and held closed until the pawl and ratchet drivemechanism has ceased to operate, trimmer condensers 20, 26, and 32 willbe connected across the front, middle, and rearward units respectivelyof gang condenser I0. Similarly, depression of push button 05 effectsrotational movement of rotary switches M and 42 until trimmer condensers2|, 21, and 33 are connected to gang condenser |0. Push button switch 91connects trimmer condensers 22, 28, and 34 to gang condenser I0; pushbutton switch 98 connects trimmer condensers 23, 29, and 35 to gangcondenser I0; and push button switch 99 connects trimmer eondensers 24,30', and 36 to gang condenser I0.

It is to be noted that push button switch 94 is associated withstationary contacts 48, 54, and 1| of switches 4| and 42, which contactsare not electrically connected to any special equipment. Preferably,contacts 48, 54, and 1| are left open circuited so that when it isdesired to remove the effect of the automatic frequency selectingequipment from the high frequency apparatus, it is simply necessary todepress push button switch 94 which moves conducting tongues of switches4| and 42 into engagement with stationary contacts 48, 54, and 1|.

Referring now to Figures 2 and 3 of the drawings, the specific structureof one form of stepping mechanism embodying the principles of thepresent invention will be described. The frame of the automatic selectorswitching mechanism is made from a one-piece stamping Idt and includesan upright partition I02, an integral solenoid base portion I03 whichextends substantially perpendicular from the lower edge of partitionI02, and an integral solenoid end wall and armature support I04 whichextends substantially perpendicular from partition I02, as shown inFigure 2 of the drawings. The solenoid 08 of the selector switchingmechanism is mounted in an upright position on base I03 in closeproximity to end wall I04. Solenoid 88 is provided with the usual ironcore I05 for the purpose of greatly increasing the effective magnetizingforce of the solenoid.

A solenoid armature 89 is mounted for limited angular movement above theupper end of solenoid 88. Armature 89 may be pivotally secured to endwall I04 in any suitable manner, it being remembered that only a verylimited angular movement is necessary to effect desired operation of thearmature. One simple method of securing armature 89 to end wall I04which has been found extremely satisfactory in practice is to slot theupper edge of end wall I04, into which slot I06 a cut-out neck portionI01 is disposed (see Fig- The upper projections I08 and ures 4 and 5).

Hi9 which define slot I06 may be peened over the neck portion I01 ofarmature 89 after the armature 89 is disposed within slot I06 to preventsubsequent removal thereof.

The outer end of armature 89 is turned upwardly as at IIO to permitsecurement thereon of drive pawl 90. Drive pawl 90' may be secured toend portion ||0 of armature 89 in any suitable manner, such as by meansof a bolt II I.

Armature 89 also includes an integral downwardly extending portion ||2which terminates a forwardly extending portion II3. Armature biasingspring I00 connects the lower end N3 of downwardly extending portion M2to a tab i 24 which is bent forwardly from the upper edge of partitionI02 and is thereby integral therewith. It will thus readily be seen thatby providing this downwardly extending portion II2 on armature 03, amuch more compact structure is obtained, since tab N4 of partition I02may be disposed much closer to armature 89 than would otherwise be thecase.

Armature 89 carries on its upper surface a leaf spring contact 9| whichis secured to armature 89 through insulating blocks H5 and H6. Leafspring contact 9| is arranged to engage an adjustable stationary contact92 when armature is in its uppermost position; that is to say, whensolenoid 88 is not exerting any downward force on armature 89.

A ratchet wheel II1, which is adapted to be engaged by pawl 90, issecured on shaft 41. Shaft i? is freely mounted in a bearing collar IIOcarried in partition I02 of frame IOI. It will thus be apparent that aspawl moves downwardly into engagement with one of the teeth of ratchetwheel H1, shaft 41 is rotated through a small angle, depending of courseupon the range of movement of the end of pawl 90' after it engages atooth on ratchet wheel II1.

The stationary contacts of switches 4|, 42, and 43 are mounted ontwoinsulating blocks I I9 and E20, which are secured to partition I02 offrame Itil by a support arm I2| which extends through partition I02.Ring blocks II9 and I20 may be conveniently secured to support arm |2|by means of a long bolt I22 which extends through support arm. |2| and acooperating nut 23. Upon close inspection of Figure 3 of the drawings,it

will be observed that stationary contacts 48 to 5d inclusive of switch4| are disposed. on the outer side of insulating block H9. Only two ofthe stationary contacts 52 and 58 of switch 4| have been shown in Figure3 for purposes of simplicity of illustration, but it will of course beunderstood that twelve stationary contacts substantially equally spacedare secured to insulating block H9 as is indicated in Figure l of thedrawings. Although not illustrated in Figure 3, it will also beunderstood that the two elongate stationary contacts 66 and 61 arearranged on insulating block I I9 in such a manner that they engage theconducting rings 62 and 64.

The short stationary contacts II to it inclusive of switch 42 and theelongate stationary contact 11 are mounted on the inner side ofinsulating block I20. Although only the elongate stationary contact 11is shown in Figure 3, it will of course be understood that the shortstationary contacts H to 16 inclusive are disposed about insulatingblock I20 in the manner indicated in Figure l of the drawings.

The stationary contacts 8! to 86 of switch 43 and elongate stationarycontact 81 of switch 43 are similarly disposed on the outer face ofinsulating block lit (see Figures 3 and 4). The general configuration ofthe stationary contacts of all three rotary switches 4!, 42, and 43 willbe understood from an inspection of Figure 2 of the drawings, it beingunderstood that the stationary contacts of each rotary switch aresimilar in configuration.

The movable contact elements 44, 45, and 46 of rotary switches 4!, l2,and 33 are secured to two insulating blocks 52% and 125 which aresecured to shaft 4?. As will be seen from an inspection of Figure 3 ofthe drawings, insulating blocks i2 1 and liii are disposed withincircular apertures in insulating blocks H9 and i251, the apertures beingsufficient in size to permit free rotation of blocks i2 2 and H25therein.

In order to prevent movement of ratchet i H in the wrong direction, astop pawl I26 is provided to engage the opposite side of ratchet wheelill from that of pawl 96. Stop pawl I26 may be conveniently secured bymeans of a bolt I2! to a tab 528 which is bent substantiallyperpendicular to partition Hi2 and is integral therewith.

Now one of the important features of the present invention is the mannerin which the drive pawl 96 engages ratchet wheel Ill. Referring toFigure 2 of the drawings, it will be noted that when armature 89 is inits uppermost position, the lower free end of drive pawl is disposedpart way between two adjacent tooth spaces. It will thus be observedthat as drive pawl $5] begins to move downwardly it does not engage atooth on ratchet wheel ll'l until it has moved a fractional part of thetooth pitch. As drive pawl 9E1 continues to move downwardly, the lowerend thereof engages a tooth on ratchet wheel ill and advances it to theposition indicated in the dotted line. This arrangement of drive pawl8E3 with respect to the ratchet wheel 5 ll permits the armature 89 toget into motion before it has to do work upon the ratchet wheel Hl. Thisarrangement permits the use of a much smaller solenoid for actuating thearmature 89 than would otherwise be necessary if the drive pawl 90 hadto immediately start to do work upon the ratchet wheel lii when thesolenoid is energized.

The operation of my automatic frequency selector will now be described.Assuming for the moment that the five diiferent frequencies at which thehigh frequency apparatus is most used are f1, f2, f3, f4, and f5, thegang condenser H3 is adjusted so that the rotors ll, l2 and I3 are intheir uppermost position, that is, outside of the stator plates id, !5and i5. Trimmer condensers 2t, 25 and 32 are then adjusted so that thehigh frequency apparatus operates at frequency f1; trimmer condensers2i, 2? and 33 are adjusted so that the high frequency apparatus operatesat frequency f2; trimmer condensers 22, 23 and 3 5 are adjusted forfrequency is; trimmer condensers 23, 29 and 35 are adjusted forfrequency f4, and trimmer condensers 24, 3E) and 36 are adjusted forfrequency is.

Assuming now that it is desired to operate the high frequency apparatusat frequency is. The push button switch 91 is depressed, thereby causingenergization of the solenoid 88 which in turn causes vibratory movementof the armature 89, thereby effecting rotation of the shaft 47. The

push button switch Si! is held depressed until the vibration of armature85 ceases, this event occurring when the cut-out portion it comes intoposition opposite the stationary contacts 84% of the rotary switch 43.At this time, the conducting tongue 70 of the rotary switch 62 is inengagement with the stationary contacts i l, thereby connecting thetrimmer condenser '34 into operative position in the circuit of the highfrequency apparatus. The conductor tongue 65 is likewise moved intoposition in engagement with the stationary contact 5?, thereby placingthe trimmer condenser 28 into operative position in the circuit of thehigh frequency apparatus. Conducting tongue 53 similarly moves intoengagement with the stationary contacts 55, thereby connecting thetrimmer condenser 22 to the high frequency apparatus. The frequency ofthe high frequency apparatus has now been changed from its originalvalue to frequency is.

Assuming now that it is desired to change the frequency setting from f3to ii. The push button switch is depressed and held down until thevibratory action of the armature 69 has ceased. At this time, thecut-out portion 8% of the switch 43 will be opposite the stationarycontact the conducting tongue 58 of the switch 1-2 will be in engagementwith the stationary contact l2; the conducting tongue 63 of the switch45 will be in engagement with the stationary contact 55; and theconducting tongue 65 will be in engagement with the stationary contactM. This arrangement of the rotary switches ll, 52 and 13 causes trimmercondensers 2d, 2 3 and to be connected in operative positions to thegang condenser l9.

Assume that it is now desired to operate the high frequency apparatus bymeans of the gang condenser It. The push button switch 94 is depressedand held in closed position untii the vibratory action of the armature89 has ceased. At this time, the movable contact elements 45 and 56 ofthe switches ll, '52 and 63 will be in the position shown in Figure l ofthe drawings. Since the conducting tongues 63', and iii are inengagement with stationary contacts and H, which are open circuited, itis obvious that all of the trimmer condensers have been removed fromoperative circuit engagement with the gang condenser Id. The gangcondenser iii may now be operated in the usual manner.

From the above description, it will be apparent that I have provided anextraordinarily simple, compact auxiliary automatic frequency selector,which may readily be connected to any high frequency apparatus. Byproviding adjustable trimmer condensers, any five frequencies which aredesired by the user of the high frequency apparatus may be set up on theautomatic frequency selector unit. It will also be understood that,because of the supreme simplicity of the construction, the automaticfrequency selector is economical to manufacture.

While I have shown a particular embodiment of my invention, it will ofcourse be understood that I do not wish to be limited thereto, sincemany modifications may be made, and I therefore contemplate by theappended claims to cover all such modifications as fall within the truespirit and scope of my invention.

I claim as my invention:

1. In an automatic selector switching mechanism of the type having asolenoid, an armature adapted to be actuated by said solenoid, a biasingspring for said armature, a pawl secured to an outer end of saidarmature, and a ratchet wheel adapted to be moved by said pawl, a frametherefor made from a single stamping having an upright partition adaptedto carry said ratchet wheel, an integral base portion extendingsubstantially perpendicular to said partition and adapted to supportsaid solenoid, an integral solenoid end wall and armature supportextending substantially perpendicular to said partition, the lower endof which is disposed in close prox imity to one edge of said baseportion, and an integral upper tab extending substantially perpendicularto said partition adapted to have said biasing spring secured thereto.

2. In an automatic selector switching mecha nism of the type having asolenoid, an armature adapted to be actuated by said solenoid, a biasingspring for said armature, a pawl secured to the outer end of saidarmature, and a ratchet wheel adapted to be moved by said pawl, a frametherefor made from a single stamping comprising an upright partitionadapted to carry said ratchet wheel, an integral base portion extendingsubstantially perpendicular to said partition and adapted to supportsaid solenoid, an integral solenoid end wall and an armature supportextending substantially perpendicular to said partition, the lower endof which is disposed in close proximity to one edge of said baseportion, an integral upper tab extending substantially perpendicular tosaid partition adapted to have said biasing spring secured thereto, anda second integral tab extending substantially perpendicular to saidpartition in close proximity to another edge of said base portion, saidsecond tab being adapted to carry a stop pawl for said ratchet wheel.

3. A rotary switch operating mechanism comprising a side plate, a flangealong one edge of said plate, a second flange along an adjacent edge ofsaid plate and forming a corner with said first flange, a solenoid insaid corner having a core parallel to said plate and said first flange,a shaft bearing carried by said side plate beside said solenoid andperpendicular to said side plate, a shaft in said bearing, a ratchetwheel on the shaft, an armature pivotally mounted on said first flangeand extending across the end of said core away from said second flange,said flanges and core and armature forming a magnetic circuit, and apawl operatively connected to said armature and placed to rotate saidwheel upon reciprocation of said armature.

4. A rotary switch operating mechanism comprising a side plate, a flangealong one edge of said plate, a second flange along an adjacent edge ofsaid plate and forming a corner with said first flange, a solenoid insaid corner having a core parallel to said plate and said first flange,a shaft bearing carried by said side plate beside said solenoid andperpendicular to said side plate, a shaft in said bearing, a ratchetwheel on the shaft, an armature pivotally mounted on said first flangeand extending across one end of said core, said flanges and core andarmature forming a magnetic circuit, a pawl carried by the armature andengaging said ratchet wheel, a lug extending perpendicular to said plateclose to said armature on the opposite side thereof from said solenoidand said ratchet wheel, an arm on said armature extending away from saidlug alongside of said solenoid and said ratchet wheehand a springconnecting said arm and said lug to resiliently urge said armature awayfrom said solenoid.

5. An electrically operated rotary switch comprising a side plate, aflange along one edge of said plate, a second flange along an adjacentedge of said plate, said flanges forming a corner, a solenoid in saidcorner having a core perpendicular to said second flange and parallel tosaid side plate and said first flange, an elongated shaft bearingcarried by said side plate beside said solenoid and perpendicular tosaid side plate, a shaft in said bearing, a ratchet wheel on the shaftadjacent said bearing, rotary switching mechanism on the shaft andspaced from said ratchet Wheel, an armature pivotally mounted on saidfirst flange and extending across the end of said core, said flanges andcore and armature forming a magnetic circuit, a pawl carried by thearmature and engaging the ratchet wheel, a lug extending perpendicularto said side plate close to said armature on the opposite side thereoffrom said solenoid and said ratchet Wheel, an arm on said armatureextending away from said lug alongside of said solenoid and between saidratchet wheel and said switching mechanism, and a spring connecting saidarm and said lug to resiliently urge said armature away from saidsolenoid.

ELMER LESLIE HOFFMANN.

